Several theoretical studies on copper oxide ore processing (2)

(III) Application of branch flotation in the flotation of copper oxide ore According to relevant information, branch flotation has a significant effect on low grade ore. Valley Copper Mine ore grade is low, small rate of fine mineral, flotation matches the branch, the branch in order to verify the adaptability of such ore flotation process, the oxidation rate were recorded at a number of 43.19%, 0.33% of the ore grade ore.
The test procedure is the same as that of the sulfide ore. See the figure below. The test results are shown in the table below.

The test results confirmed that branch flotation is effective for oxidized ore low grade ore. Concentrate re-grinding improves the concentrate grade by 5% consistent with sulfide ore, indicating that the coarse concentrate regrind process is applicable to copper ore and ore. [next]
The branch flotation process is suitable for ore with low grade and low concentrate yield of copper ore and also suitable for oxidized ore. The combination of the branch flotation process and the coarse concentrate regrind process can save 10-15% of various chemicals and increase the concentrate grade by 4~5%. The overall economic effect is very significant, and it is one of the ways to reduce the cost of mineral processing and improve economic efficiency.
(iv) Mechanism of replacing copper from cholesteric solution with iron powder In many methods for directly precipitating copper from solution (eg electrolysis, displacement with iron , aluminum or zinc ; with CO, H ₂ , H ₂ S or SO ₂ precipitation; and precipitation with Ca(OH) ₂ or CaCO ₃ ) has proven to be economically feasible only with iron displacement methods for low concentration, multi-impurity solutions.
China's Jiangxi Copper Company has used copper extraction or electrowinning or lime precipitation to recover copper. The economic benefits of the iron powder replacement method have gradually been recognized. Therefore, it is still of practical significance to further elaborate the iron powder replacement technology through theoretical analysis and scientific experiments. The Beijing Research Institute of Mining and Metallurgy has written and discussed methods for iron powder replacement technology, process requirements, reduction of iron consumption and obtaining high-purity copper powder.
1. The relationship between the pH value of the copper ion replaced by iron and the displacement rate. As the pH of the solution decreases (the free acid increases), the exchange rate increases, and there is no free acid in the solution, it is difficult to exchange; ²⁺ content decreased, the exchange rate also slows down, and finally dissolved the precipitate in equilibrium, the exchange rate does not rise, to keep this balance iron depletion; suitable pH and metal iron vitriol is exchanged 2~2.5.
Relationship between replacement time and exchange rate As the replacement time increases, the exchange rate increases, but the speed decreases (due to a decrease in Cu ²⁺ concentration and a rise in pH). When the positive reaction and the reverse reaction are balanced, the exchange rate reaches the highest value. Until the metal iron is exhausted; after the metal iron is completely dissolved, the excess free acid in the solution causes the precipitated copper to be slowly dissolved again, causing the copper in the discharge liquid to rise and the exchange rate to decrease. Therefore, it is extremely important to have a correct grasp of the chemical balance.
Relationship between iron powder dosage and displacement rate In the same exchange time, the more the reduced iron powder is used, the faster the exchange speed; when the pH value of the solution exceeds 4, the exchange rate no longer rises. When there is excessive metal iron in the solution, it can prevent the Cu ^{2+ from} rising in the solution, but the excessive amount of iron powder will lower the grade of precipitated copper and increase the acid consumption.
The effect of the copper content of the solution on the exchange The higher the Cu ²⁺ concentration in the solution, the higher the exchange rate. Therefore, in practical applications, the concentration of the liquid should be increased as much as possible; the collision frequency of Cu ²⁺ and Fe° is increased and the FeSO _{4 is} increased. Measures to spread the speed in order to speed up the exchange and obtain a higher listening exchange rate.
Countercurrent exchange test The countercurrent exchange method can obtain high-grade precipitated copper and high auditing exchange rate while approaching the theoretical iron loss.
The test conditions were 5 g of copper per liter of liquid, pH 2, the amount of reduced iron powder was 110% of theoretical iron consumption, and the exchange time was 15 minutes. The test results were calculated in the table below.

    The concentration of hydrogen ions in the solution decreases, the exchange rate slows down, the copper content of the effluent increases, and the exchange rate and the grade of precipitated copper decrease. Therefore, the change of hydrogen ion concentration and the timely addition of free acid should be strictly monitored during the exchange process. In the exchange liquid; the first batch of exchange liquid theoretical iron loss 5.5 times reduced iron powder meet, according to the chemical reaction principle, its exchange rate should be the highest, but on the contrary, its discharge liquid contains copper up to 0.19 g / liter, which An "abnormal" phenomenon is extremely important and is a very meaningful enlightenment given by the countercurrent exchange experiment.
Effect of Fe ³⁺ on displacement In the sulfuric acid leaching solution of copper ore, a certain amount of ferric ions are present more or less. When replacing copper with iron powder, most of the ferric iron in the solution is reduced to divalent iron according to the reaction formula Fe ₂ (SO ₄ ) ₃ +Fe→3FeSO ₄ , thereby increasing iron loss and increasing iron consumption. Calculated as a complete reaction, it is one-half the amount of ferric ion in the solution. Based on the data obtained from the test, it can be concluded that when copper is replaced with iron powder, almost all of the Fe ^{3+ in the} solution is reduced to Fe ²⁺ . Thus, the switching process to prevent the oxidation of Fe ^2+, Fe ²⁺ oxidation will increase and accelerate the hydrolysis of Fe ³⁺ iron loss, harm to the replacement job. For the treatment of a solution having a high concentration of Fe ^{3 +} , it is not preferable to use an iron powder replacement method. In this case, it is necessary to consider the reduction of Fe ^{3+ in} advance.
2. Example of copper recovery by iron powder replacement method 1 Recovery of copper in acid leaching solution of Wushan copper ore Wushan comprehensive ore acid leaching solution contains 14.1 grams of copper, 7.7 grams of iron, and 0.25 grams of Fe ³⁺ in exchange. It is necessary to add 0.125 g of pure iron to each liter of solution as a means for reducing Fe ³⁺ to Fe ²⁺ . Then, 0.88 grams of pure iron is required for each gram of copper to calculate the theoretical iron loss. The pH of the solution was first adjusted to 2 with sulfuric acid, and then iron powder was added for 15 minutes with agitation. The test results are shown in the table below.

Example 2 Recovery of Copper from Copper and Zinc Ore Pickling Liquid in City Hill The Jiangxi Chengmenshan copper-zinc ore contains water-soluble copper and adsorbed copper. This part of copper needs to be eluted with dilute sulfuric acid and then recovered. The pickling solution contains 0.97 g of copper per litre. Because there is no chemical analysis data of other ions, the iron loss can only be calculated based on the copper content and expressed by the general industrial iron consumption. The pH of the pickling solution was adjusted to about 2, then the reduced iron powder was added under agitation, exchanged for 15 minutes, filtered immediately, and washed. The results obtained are listed in the table below.

The test proves that it is feasible to use the experimental results of the ideal solution to guide the exchange practice of the natural copper-containing solution.
3. Cholesterol solution iron powder copper extraction principle Iron powder replacement chemistry The three main reactions in the iron powder replacement process are:

CuSO ₄ +Fe→FeSO ₄ +Cu (1-1)

Fe ₂ (SO ₄ ) ₃ +Fe→3FeSO ₄ (1-2)

H ₂ SO ₄ +Fe→ FeSO ₄ +H ₂ (1-3)[next]

When the pH is 2 to 2.5, the formula (1-1) is the main reaction in the case of agitation, and the formula (1-2) becomes important in the case of the stationary state, and the dissolution rate of the iron is accelerated when the pH is <2. . The precipitated metallic copper is also reversely dissolved during the replacement process, and slowly dissolves in the aerated acid solution according to (Formula 1-4), but dissolves faster in the ferric sulfate solution (Formula 1-5).
1
Cu + H ₂ SO ₄ + — O ₂ → CuSO ₄ + H ₂ O (1-4)
2

Cu+Fe ₂ (SO ₄ ) ₃ → CuSO ₄ +2FeSO ₄ (1-5)

Hydrolysis and oxidation of Fe ²⁺ to Fe ^3+: when dissolved iron sulfide ore and other minerals, and some iron oxide minerals during leaching, Fe ³⁺ is reduced to give a considerable amount of Fe ^2+, and Fe ^{3+ is} easily oxidized to Fe ³⁺ :

4FeSO ₄ +O ₂ +2H ₂ SO ₄ →2Fe ₂ (SO ₄ ) ₃ +2H ₂ O (1-6)

When the Fe ³⁺ Fe ²⁺ formed oxidation exceeds the solubility, or pH increase, ferric Click (1-7) is hydrolyzed to achieve a new equilibrium.

Fe ³⁺ +3H ₂ O ←→Fe(OH) ₃ +3H ⁺ (1-7)

Controlling the pH of the solution to prevent the precipitation of Fe(OH) _{3. The} ferric iron is inevitably produced during the immersion process, and is very harmful to the precipitation replacement. Therefore, the precipitation of Fe(OH) _{3 is} prevented, and the precipitation of biliary water is prevented. The success or failure of copper operations is very close. The pH of Fe(OH) ₃ precipitation is related to the concentration of Fe ³⁺ ion. When the pH of the solution exceeds 3.7, the Fe ³⁺ ion concentration in the solution is very low (10 ^-5 M), and it is also precipitated by hydrolysis and precipitated. (OH) ₃ solids entering the precipitated copper reduce the grade of precipitated copper, hinder the reduction of copper ions by iron and reduce the rate of displacement. Therefore, when copper is reduced with iron, the pH optimum control range of the solution starts at ±2 and ends at ±3.
Bronze iron powder kinetics The reaction of iron powder replacement occurs at the solid-liquid interface, and the chemical interaction causes the concentration of the interface and the solution to differ, causing diffusion. However, this concentration is only present in a relatively liquid film (diffusion layer) which is in close contact with the solid surface, and the inside of the solution is uniform. A continuous change in solution concentration occurs within the diffusion layer, the reactant diffuses toward the interface through the diffusion layer, and the product exits the interface through the diffusion layer.
Thus, the reaction of iron powder replacement involves two steps of diffusion and interfacial chemical reaction. Experiments have shown that the chemical reaction at the phase interface proceeds very quickly, and the diffusion rate is slow, which becomes a barrier to the reaction. Therefore, the total speed of the process depends on the diffusion rate.
The whole reaction speed V _{0 of} copper iron powder is equal to:

D•A
Vo = ———• △C (1-8)
V•δ

Where V is the volume of the solution and ΔC is the increment of the concentration on both sides of the diffusion layer.
Formula (1-8) shows that the solid-liquid reaction rate depends on the diffusion coefficient D, the phase interface area A and the thickness of the diffusion layer δ. Any measure that can change these factors can change the reaction rate.
In the iron powder replacement operation, attention should be paid to the following problems: (1) reducing the particle size of the iron powder, (2) temperature, (3) stirring, (4) acidity of the solution, and (5) concentration of bile water.
Through the experiments on the ideal solution and the actual aqueous solution, and the discussion on the mechanism of copper extraction from the bile water iron powder, it is shown that as long as the reasonable process and the process influencing factors can be detected and adjusted in time, it can be close to the theoretical value. Iron consumption, high exchange rate and high grade precipitated copper.

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